1. Field of the Invention
The present invention relates to a wheelchair for single-hand operation that can be classified into several different kinds of operation methods and is capable of moving forward and backward and controlling the moving direction with one hand.
2. Prior Art
There are several different kinds of wheelchairs that can be operated with a single hand. One type that is generally used is made such that the moving direction is controlled by individually operated driving wheels on both sides with double rings established on the working-hand-side of the wheelchair. This makes it very difficult to simultaneously apply individual movement to each wheel; therefore, it is impossible to change directions smoothly. Transmission of power to the driving wheel which is on the opposite side of the working-hand side via a joint is not very efficient, resulting in a poor balance between the left and right driving wheel and adding to the difficulty of operation. As a result, experience and skills are required for smooth operation of the wheelchair.
Another type of wheelchair employs an operation lever on the working-hand side linked with a mechanism using a one-way clutch (one-way drive clutch) that switches between forward and backward movements. This type employs another lever established at the tip of the operation lever, which activates a caster yoke linked with a caster wheel, to change the moving directions. While this type excels in direction-changing performance, it requires a switching operation between forward and backward movements. As such, there is merit and demerit in both types mentioned above.
Still another type of wheelchair was invented by the applicant of the present invention and was patented in Japan as Japanese Patent No. 1,330,760. This type employs a single operation lever that drives both left and right driving wheels and a differential link mechanism that applies a driving difference to change moving directions. In this wheelchair, switching between forward and backward movements is automatically performed across the neutral position, and the clutch also functions as a brake to make the operation quite easy. The operation lever has only to be moved in the intended direction. This type requires minimum skill; therefore, it is especially suitable for physically weak people who have poor judgment.
The lever-operated wheelchair, on the other hand, is somewhat difficult for a ring-type wheelchair user because of its rather awkward shape, thus a ring-type wheelchair which is easy to operate is desirable.